Could be a bad sender. I suggest watching the gauge and your miles for a while and see what happens.

it also goes down when i step on the gas sometimes. haha i guess im going to start calculating things again haha.

my gauge sits on full all day every day it sucks but you have to drop the tank to fix it i just count the miles lol

What year is your car again? having that in your sig helps us. You could have a bad baffle in the tank too.

just for added info... when i completely top mine off it wont come off the full mark for at least the first 75 miles... and i have a new sender and level unit... so if its possible its accurate... im also having a 02 circuit problem so im not getting perfect fuel mileage

drive it, watch your miles, and once you get to a 1/4 tank... fill her up completely... if your around 12-14 gallons to fill up your about right on the sender and level unit... if you get to half a tank and it cuts out and dies due to no gas... your a SOL *sorry* and will need to replace, level unit or sensor.
i think lol dont quote me... i dont want to be blamed... just my 2 pennies

once it gets low to like half a tank... go around a couple turns quickly and see if it cuts out... mine did that and i had to replace the sender to fix... replaced the level unit while it was out

The sending unit often goes bad in these GMs. You have to drop the gas tank to replace it, but I'd much rather get used to a faulty fuel gauge. Make sure your fuel pump works at a factory-intended PSI. If not, drop the tank to replace your pump and change out the sending unit at the same time.

aw damn im not dropping the tank ill just get used to counting it. i thought it would be like my old car. my car is 95. will put that up in my sig.

How many gallons is the stock tank?

17.9 Gallons.

well i calculated 22mpg(325miles/15gallons).. and about, 300 of that was highway. is this normal? i could kind of smell something if i brake or park after driving.. its not really gas smell, it smells like something else with a hint of gas. i dont know if that makes sense?